Means for connecting electrical appliances to power lines



March 6, 1934. w K, FLEMlNG 1,949,996

MEANS FOR CONNECTING EIJEGTRICAI.;` APPLIANCES T0 POWER LINES Filed Nov.2'4",y 1928 Patented Mar. 6, 1934 UNITED STATES PATENT QFFICE MEANS FORCGNNECTING ELECTRICAL APPLIANCES TO POWER LNES Wilfred K. Fleming,

Canton, Mass.,

assigner Application November 27, 1928, Serial No. 322,243

3 Claims.

This invention relates to means for connecting an electrical appliance,such as a motor, to the power lines of a building, and aims to providemeans for preventing the appliance irom setting up interference withradio reception. The invention may be variously embodied in connectorsof different kinds, and in switches i'or controlling the electricalappliances.

The invention will be best understood by reference to the followingdescription, when taken in connection with certain embodiments disclosedin the accompanying drawing, while its scope will be more particularlypointed out in the appended claims.

In the drawing:

Fig. 1 is a sectional view of a plug-in connector embodying theinvention;

Fig. 2 is a plan of the upper end of the saine;

Fig. 3 is an electrical diagram of the connector disclosed in Figs. land 2;

Fig. 4 is a sectional View of a cord switch embodying the invention;

Fig. 5 is an electrical diagram of the switch disclosed in Fig. 4; and

Fig. 6 is an electrical diagram illustrating a modification of thedisclosure of Fig. 3.

Referring to Figs. 1, 2 and 3, of the drawing, and to the embodiment ofthe invention which is illustrated therein, there is shown a connectorcomprising a casing composed of two end caps l0 and 1l oi insulatingmaterial, connected to cach other by a tubular sleeve or shell 12, alsoof insulating material, the three parts being securely connected to eachother, as by a rod 13 threaded at one end into a nut 14 anchored in thecap 11, and at its other end into a nut 15, which may be unscrewed fromthe rod to permit the device to be dismounted. The casing houses a pairof conductors 16, which extend through apertures 1'7 in the cap 11, andpresent prongs 18 to be plugged into a socket. The cap 11 is providedwith chambers 19, which receive contacts 20, suitably attached as byscrews 21 to the conductors 16. The cap is further provided withapertures 22 for the insertion of usual conducting prongs, similar tothe prongs 18, into the chambers 1Q for engagement with the springcontacts 20.

The casing houses two fixed condensers 23, one of which is shown in Fig.1, as it is behind the plane of the section, but the other is not shown,because it is in front of said plane. However, both condensers are showndiagrammatically in Fig. 3. Each condenser has one terminal 24,connected to one of the conductors 16, and each has a second terminal25, these two terminals being connected to each other,-that is to say,the condenser-s are in series, and are connected across the powerconductors. In practice, it is found that if each condenser has acapacity of from .G2 microfarads to 2. microfarads, satisfactory resultsare achieved. Heretofore, it has been generally supposed thatinterference-preventing condensers must have very large capacities, andhence must be of considerable size, but l have found that condensers ofthe capacities which I have mentioned are ample to avoid the setting upor interference with radio reception.

many instances, the device as thus far described is all that isnecessary to ground out the interference set up by the electricalappliances. especially w'pere the connector can be applied very close tothe electrical appliance. In other instances where the interference issevere, a conductor 26 connected between the two condensers and leadingfrom the casing for attachment to the frame of the motor or otherappliance will eliminate interference.

While the use of the described condensers, especially when used inconnection with the third conductor for attachment to the motor frame,will suiiice in most cases to eliminate interference, it is desirable touse in some extreme cases chokes or iinpedances 27 (see Fig. 6) in theline wires or conductors, and these impedances should be placed behindthe condensers,-that is to say, between the condensers and the currentsource. The value of these chokes may vary, but can be between .002 to.01 milhenries. It should be understood that the use of these chokes isfor a case oi extreme interference, where the condensers alone will notsuce.

Figs. 4 and 5 show the application of the invention to a cord switch,having a casing 28 provided with a chamber 29, which houses a switchmechanism of common form, comprising two binding posts 30, two iiXedcontacts 31, a movable switching contact 32, and a plunger 33, havingpush buttons 34, which project through the sides of the casing. Itshould be understood, of course, that the switch mechanism operates inthe usual manner to make and break a connection between the Xed contacts31.

The casing is provided with passages 35, leading from the chamber to theends of the casing for cords 35, each containing a conductor 37 and aconductor 38. rThe conductor 37 extends entirely through the chamberwithout break, although in the drawing, it is shown as broken todisclose the switch mechanism. The ends of the conductors 38 areattached to the binding posts 30.

The casing houses two condensers 39 like those previously described, andin like manner connected to each other in series, and connected acrossthe conductors 37 and 38. In this case, also, there is provided a thirdconductor 40 connected to the mid-point between the condensers, andleading from the casing for attachment to the frame of the motor orother appliance. In the form shown in Fig. 4, the condensers 39 areconveniently placed with two of their edges abutting along a line behindthe switch mechanism. The condensers have usual terminals 41 and 42 forattachment to the conductors.

In connection with the use of the two condensers and the third conductorconnected to the mid-point between them, it should be understood thatthis is done because the frame of the motor or other appliance must notbecome common to either side of the line. In other words, if onecondenser were used from the positive side of the line, then the frameof the device to which the other side of the condenser would beconnected would have to be common to the other or negative side of theline. This is not good practice; as the frame should always be insulatedfrom both sides of the line. Furthermore, if only one condenser wereused from the line to the frame of the device, it would be necessary touse a polarized receptacle for the input cord of the device, in orderthat the condenser would always be on the positive side of the line. Bythe use of the two condensers and the third conductor, it is unnecessaryfor the user to shift the plug from one side to the other of the line,to be sure that he is connecting the apparatus into the line in thesaine way.

Having thus described one embodiment of the invention, but withoutlimiting myself thereto, what I claim and desire by Letters Patent tosecure is:

1. In a unitary connector for connecting an electrical appliance to thepower lines which supply the appliance and for suppressingradio-frequency oscillations set up by the appliance, the combination ofa casing comprising two menibers, each provided with two passages, saidcasing being provided with a chamber between the passages of one memberand the passages of the other member, a rod within said chamberconnecting said members to each other, two conductors for the two sidesof the power circuit, said conductors being located partly in saidchamber and partly in the passages of each of said members, and meanswithin said chamber for suppressing radio-frequency oscillations set upby the appliance.

2. In a unitary connector for connecting an electrical appliance to thepower lines which supply the appliance and for suppressingradio-frequency oscillations set up by the appliance, the combination ofa casing comprising two members, each provided with two passages, saidcasing being provided with a chamber between the passages of one memberand the passages of the other member, a rod within said chamberconnecting said members to each other, two conductors for the two sidesof the power circuit, said conductors being located partly in saidchamber at opposite sides, respectively, of said rod, and partly in thepassages of each of said members, and means within said chamber forsuppressing radiofrequency oscillations set up by the appliance.

3. In a unitary connector for connecting an electrical appliance to thepower lines which supply the appliance and for suppressingradiofrequency oscillations set up by the appliance, the combination ofa casing comprising two members, each provided with two passages, saidcasing being provided with a chamber between the passages of one memberand the passages of the other member, a rod within said chamber

